Sheet feeding device and image forming apparatus

ABSTRACT

A sheet feeding device includes a regulation member having a sheet-regulation surface, and an air blowing mechanism. The regulation member regulates the positions of sheets that are stacked on a sheet stacking device. The air blowing mechanism raises the sheets by blowing air onto an edge of a stack of the sheets that are stacked on the sheet stacking device. The regulation member is formed so that air that is blown from the air blowing mechanism passes the regulation member, thereby overcoming the problem of the flow of sheet-loosening air and sheet-separation air being disturbed by the regulation member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet feeding device and an imageforming apparatus, and, more particularly, to a sheet feeding device andan image forming apparatus which feed sheets by separating the sheets asa result of blowing air onto the sheets.

2. Description of the Related Art

A related image forming apparatus, such as a copying machine or aprinter, includes a sheet feeding device that feeds sheets to an imageforming device by separating them one at a time from a topmost sheet ofthe sheets that are stacked on sheet stacking means.

One type of such a sheet feeding device feeds sheets by an airsheet-feeding method. In the method, air is blown onto an edge of astack of sheets that are stacked on the sheet stacking means to raisethe plurality of sheets and loosen them from each other. Then, thetopmost sheet is attracted to an attracting conveying belt and fed. Thesheet feeding device of the type that uses the air sheet-feeding methodis, particularly, suited for high-speed sheet feeding, so that it isfrequently used in high-speed apparatuses. For example, Japanese PatentLaid-Open No. 5-61305 discloses a sheet feeding device that uses the airsheet-feeding method.

FIG. 8 is a schematic sectional view of a related sheet feeding devicethat uses the air sheet-feeding method.

As shown in FIG. 8, a sheet-feed deck 401 that holds sheets P has a tray403. The tray 403 is used to stack the sheets P therein and can beraised and lowered in accordance with the number of sheets. The sheets Pare held at predetermined positions by side regulation plates 457, arear-end regulation plate 458, and a front-end regulation plate 456. Theside regulation plates 457 and the rear-end regulation plate 458 aremovable in a sheet width direction and a sheet-feed direction so thatthey can be used with sheets of various sizes.

An attracting conveying belt 407 is provided above the sheet-feed deck401, and can rotate in the sheet-feed direction that is indicated by anarrow in FIG. 8. The belt 407 attracts the topmost sheet of the sheets Pthat are stacked in the tray 403, and transports the topmost sheetdownstream. A suction duct 492 that causes negative pressure to act forattracting the topmost sheet by suction air from a suction fan (notshown) is provided at an inner side of the attracting conveying belt407.

A sheet-loosening air nozzle 494 is provided downstream from thesheet-feed deck 401. The air nozzle 494 is used to loosen a stack ofsheets as a result of raising the stack of sheets by blowing air onto afront-side edge of the stack of sheets that are stacked in the tray 403.To prevent double feeding, a sheet-separation air nozzle 493 thatsupplies sheet-separation air for separating a next sheet from thetopmost sheet that is attracted to the attracting conveying belt 407 isprovided.

When feeding the sheets, the sheet feeding device having such astructure loosens the sheets as a result of blowing sheet-loosening airfrom the sheet-loosening air nozzle 494 onto the front-side edge of thestack of sheets. At the same time, suction air is made to act upon thetopmost sheet to attract the topmost sheet to the attracting conveyingbelt 407. Further, the sheet-separation air from the air nozzle 493separates the next sheet from the topmost sheet that is attracted to theattracting conveying belt 407.

The air from the sheet-loosening air nozzle 494 and the air from thesheet-separation air nozzle 493 cause a plurality of upper sheets of thestack of sheets to be raised and pushed rearward. However, the rearwardmovement of the upper sheets is stopped by the rear-end regulation plate458. Accordingly, the rear-end regulation plate 458 has a height thatdoes not allow the sheets that are moved rearward to move over therear-end regulation plate 458. More specifically, the rear-endregulation plate 458 is at least higher than a surface of the attractingconveying belt 407 that attracts the sheets.

Rotating the attracting conveying belt 407 after attracting only thetopmost sheet to the attracting conveying belt 407 makes it possible totransport topmost sheets one at a time and downstream by the attractingconveying belt 407 while preventing double feeding.

In the air sheet-feeding method, the air that is blown onto the edges ofthe sheets pass between the sheets of the sheet stack, so that thesheets are reliably raised and loosened. Accordingly, to reliably loosenthe stack of sheets, the air needs to flow in a laminar state betweenthe sheets of the sheet stack.

In the related sheet feeding device and image forming apparatus, whenair that is blown onto and acting upon the sheets passes through thestack of sheets, and, then, strikes the rear-end regulation plate 458, adisturbance is produced in the flow of air, in which case, the air fromthe sheet-loosening air nozzle 494 and the air from the sheet-separationair nozzle 493 do not flow in a laminar state. As a result, the stack ofsheets is not satisfactorily loosened and separated. This may result indouble feeding or improper feeding.

SUMMARY OF THE INVENTION

In view of such circumstances, the present invention provides a sheetfeeding device and an image forming apparatus which can efficientlyloosen and separate sheets by air

According to the present invention, a sheet feeding device is providedwhich includes a tray adapted to support a stack of sheets, the trayfurther being adapted to be raised and lowered; a regulation memberhaving a sheet-regulation surface, the regulation member being adaptedto regulate the position of the sheet stack as a result of thesheet-regulation surface coming into contact with the sheet stack; anair blowing mechanism positioned opposing to the regulation member,wherein the air blowing mechanism is configured to blow air into anupper region of the sheet stack; and a sheet feeding mechanism adaptedto feed the top-most sheet away from the sheet stack, wherein theregulation member is configured such that the blown air passes throughan escape portion, defined by the sheet-regulation surface.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural view of a printer, which is an exampleof an image forming apparatus, including a sheet feeding deviceaccording to an embodiment of the present invention.

FIG. 2 is a plan view of a paper deck that is provided at the sheetfeeding device.

FIG. 3 is a side view of the paper deck.

FIGS. 4A and 4B show structures of a rear-end regulation plate that isprovided at the paper deck.

FIGS. 5A and 5B illustrate an example in which through holes are formedin the rear-end regulation plate.

FIG. 6 illustrates an operation of the rear-end regulation plate havingthe through holes.

FIG. 7 illustrates a flow of air when feeding sheets by the sheetfeeding device.

FIG. 8 illustrates a structure of a related sheet feeding device.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a schematic structural view of a printer, which is an exampleof an image forming apparatus, including a sheet feeding deviceaccording to an embodiment of the present invention.

In FIG. 1, reference numeral 1000 denotes a printer, and referencenumeral 1001 denotes a printer body. An image reading device 200 isprovided at the upper portion of the printer body 1001, and reads animage of an original that is sent onto a platen glass 102, serving as anoriginal table, by an automatic original feeding device 100. An imageforming device 300 that forms images on sheets P, and a sheet feedingdevice 400 that supplies the sheets P to the image forming device 300are provided below the image reading device 200. The sheet feedingdevice 400 uses the aforementioned air sheet-feeding method.

The image forming device 300 includes, for example, a photosensitivedrum 111, a developing unit 112, and a laser scanner unit 110. The sheetfeeding device 400 includes a first paper deck 401 and a second paperdeck 451, which having a common sheet-feeding mechanism, and anattracting conveying belt 407, which is a sheet-feeding mechanism forfeeding the sheets that are held in the first paper deck 401 and thesecond paper deck 451.

The sheet feeding device 400 includes air blowing units 406 which areair blowing mechanisms that are provided at a side towards which sheetstack supported by trays 403 are fed and that blow air from front-sideedges of the sheet stack. The trays 403 are provided at the first paperdeck 401 and the second paper deck 451, respectively, and will bedescribed in more detail later. The first paper deck 401 can hold 1500sheets P, and the second paper deck 451 can hold 2000 sheets P.

An image forming process of the printer 1000 having such a structurewill be described.

When a start button (not shown) is pressed, the original feeding device100 feeds upwardly facing originals, which are set in an original tray150, leftwards one at a time starting from the first page. Then, itfeeds the originals onto the platen glass 102 from the left of theplaten glass 102 through a curved path to transport the originalstowards the right via a feeding-and-reading position. Thereafter, theoriginals are discharged towards an external sheet-discharge tray 151.

When the originals pass the feeding-and-reading position at the platenglass 102 from left to right, the images of the originals are read by ascanner unit 104 that is held at a position which is in correspondencewith the feeding-and-reading position. In general, this reading methodis called an “original feeding-and-reading method.”

More specifically, when the originals pass the feeding-and-readingposition, reading surfaces of the originals are irradiated with light ofa lamp 103 of the scanner unit 104. Light that is reflected from theoriginals is guided to a lens 108 through mirrors 105, 106, and 107.Light that passes through the lens 108 is focused onto an imaging planeof an image sensor 109.

When the originals are transported so that they pass thefeeding-and-reading position from left to right, the originals arescanned for reading the originals, with a direction that isperpendicular to a direction of transportation of the originals beingdefined as a main scanning direction and the transportation directionbeing defined as a sub-scanning direction.

More specifically, the entire images of the originals are optically readas a result of transporting the originals in the sub-scanning directionwhile the image sensor 109 reads the images of the originals one line ata time in the main scan direction when the originals pass thefeeding-and-reading position. Then, the images that are optically readin this way are converted into image data by the image sensor 109, andthe image data is transmitted to the laser scanner unit 110 of the imageforming device through a memory (not shown).

The image reading device 200 can also read the originals as a result ofcausing the scanner unit 104 to perform scanning from left to lightwhile the originals that are transported onto the platen glass 102 bythe original feeding device 100 are stopped at predetermined positions.This reading method is called an “original fixing-and-reading method.”

When the originals are to be read without using the original feedingdevice 100, first, a user raises the original feeding device 100 andplaces the originals on the platen glass 102. Then, the user uses thescanner unit 104 to scan the originals from left to right, so that theoriginals are read. When the originals are read without using theoriginal feeding device 100, the “original fixing-and-reading method” isperformed.

Next, in the image forming device 300, when the image data istransmitted from the image reading device 200 to the laser scanner unit110, the photosensitive drum 111 is irradiated with laser light on thebasis of the image data from the laser scanner unit 110. At this time,the photosensitive drum 111 is previously charged. When thephotosensitive drum 111 is irradiated with the laser light, anelectrostatic latent image is formed. Then, the electrostatic latentimage is developed by the developing unit 112 to form a toner image onthe photosensitive drum 111.

When a sheet-feed signal is output to the sheet feeding device 400 froma controlling device (not shown), sheets P that are held in the firstpaper deck 401 or the second paper deck 451 are attracted to theattracting conveying belt 407 and sent out. Then, the sheets P that aresent out in this way pass through a sheet transportation unit 409, andis transported to registration rollers 115 to correct any obliquemovement of the sheets P. Thereafter, the sheets P are sent to atransfer unit, including the photosensitive drum 111 and a transferroller 116, in synchronization with the toner image on thephotosensitive drum by the registration rollers 115.

Next, the toner image is transferred onto the sheet P that has been sentto the transfer unit in this way. Then, the sheet P having the tonerimage transferred thereon is transported to a fixing unit 117. Then, thetransferred unfixed image is permanently fixed to the sheet P by heatingand applying pressure to the image by the fixing unit 117. Thereafter,the sheet P having the image fixed thereto in this way is discharged bydischarge rollers 118 and 120 to a sheet-discharge tray 119 or asheet-discharge tray 121 from the printer body 101.

FIG. 2 is a plan view of the first paper deck 401. The second paper deck451 structurally differs from the first paper deck 401 only in themaximum number of sheets that it can hold.

The first paper deck 401 includes a sheet holding unit 453 and the tray403 serving as sheet stacking unit. The sheet holding unit 453 is usedto set sheets P thereon. The tray 403 is provided in the sheet holdingunit 453 so that it can be raised and lowered, and holds the sheets P inlayers. A tray raising-and-lowering mechanism (not shown) moves the tray403 to a lowered position for replenishing or replacing sheets and to afeeding position for sending out sheets.

The first paper deck 401 also includes side regulation plates 457 and arear-end regulation plate 458. The side regulation plates 457 regulatethe positions of the sheets P, supported by the tray 403, in a widthwisedirection of the sheets P that is perpendicular to a sheet-feeddirection of the sheets P. The rear-end regulation plate 458 regulatesthe rear-end positions of the sheets P at an upstream side in thesheet-feed direction of the sheets P. The side regulation plates 457 andthe rear-end regulation plate 458, which regulate the positions of thesheets P, are formed so as to be movable in accordance with the size ofthe sheets P.

In the embodiment, sheets P having widths in the range of from B5R to14.33 inches (182 mm to 364 mm) and lengths in the range of from B5 to19.2 inches (182 mm to 488 mm) can be stacked.

To make it possible to stack the sheets P having such widths andlengths, notches 459 and 460 are provided in the tray 403 so as not toprevent the movement of the side regulation plates 457 and the rear-endregulation plate 458 in the range of movement of the side regulationplates 457 and the rear-end regulation plate 458.

In the paper deck on which the sheets P from small sheets P to largesheets P can be stacked, the location of the rear-end regulation plate458 is positioned at about the center of the paper deck in the widthwisedirection so as not to be provided at the notches 459 of the tray 403.The attracting conveying belt 407 and a suction duct 492 are alsodisposed at about the center of the paper duct in the sheet-widthdirection as shown in FIGS. 2 and 3 so as to allow sheets having thesmallest length in the widthwise direction (B5R-size sheets in theembodiment) to be stacked.

As discussed in the description of the related art, air from the airblowing unit 406 causes a plurality of upper sheets of the stack ofsheets to be raised and pushed rearward. However, the rearward movementof the upper sheets is stopped by the rear-end regulation plate 458.Accordingly, the rear-end regulation plate 458 has a height that doesnot allow the sheets that are moved rearward to move over the rear-endregulation plate 458. More specifically, the rear-end regulation plate458 is at least higher than a surface of the attracting conveying belt407 that attracts the sheets.

Further, as shown in FIG. 3, sheet-loosening air nozzles 493 for blowingout sheet-loosening air to loosen the sheets P and sheet-separation airnozzles 494 for blowing out sheet-separation air to prevent doublefeeding are provided in the air blowing unit 406 so as to be situated inthe center thereof in the widthwise direction.

In particular, the sheet-separation air nozzles 493 are for separating anext sheet from the top-most sheet that is attracted to the attractingconveying belt 407. It is preferred that the sheet-separation airnozzles 493 need be disposed at or about the same positions in thewidthwise direction as an opening of the suction duct 492 and theattracting conveying belt 407.

The separation and loosening of the sheets are performed moreeffectively when a plurality of the air nozzles 493 and a plurality ofair nozzles 494 are provided than when only one air nozzle 493 and oneair nozzle 494 are provided. Therefore, in the embodiment, as shown inFIG. 3, six sheet-separation air nozzles 493 and two sheet-loosening airnozzles 494 are provided at the central portion of the paper deck in thewidthwise direction.

When the first paper deck 401 has such a structure, as shown in FIG. 2,the center of the sheet-separation air nozzles 493 and the rear-endregulation plate 458 overlap each other in the sheet-feed direction.This means that the rear-end regulation plate 458 is provided so as tooppose the sheet-separation air nozzles 493. For this reason, after airfrom the sheet-separation air nozzles 493 flows through the sheets whilethe air acts upon the sheets, the air flows towards the rear-endregulation plate 458.

In the embodiment, as shown in FIG. 4A, an escape portion 481, which isformed by cutting away a portion of a sheet-regulation surface 458 aopposing the sheet-separation air nozzles 493, is provided. Thesheet-regulation surface 458 a is a surface of the rear-end regulationplate 458 that comes into contact with a rear edge of a sheet 491 (seeFIG. 7). The escape portion 481 allows air flowing towards the rear-endregulation plate 458 after being blown out from the sheet-separationnozzles 493 and passing through the sheets 491 to escape. Therefore, nodisturbance is produced in the air, so that the air is in an ideallaminar state as shown in FIG. 7.

As shown in FIG. 4A, when through holes (escape portion) 481 a areformed in the sheet-regulation surface 458 a, the air passes therear-end regulation plate 458 from the through holes 481 a, so that thelaminar state is more effectively produced.

When the escape portion 481 is provided in the rear-end regulationmember 458 so that the air from the sheet-separation air nozzles 493passes the rear-end regulation member 458, the problem of the rear-endregulation plate 458 disturbing the flow of the sheet-loosening air andthe sheet-separation air can be prevented from occurring. Therefore, itis possible to produce a laminar flow of blown air, and to efficientlyloosen and separate the sheets P by the air without loss of air.

In the embodiment, the escape portion 481 is provided by cutting away aportion of the sheet-regulation surface 458 a of the rear-end regulationplate 458 that opposes the sheet-separation air nozzles 493. However,when the rear-end regulation plate 458 has a portion that opposes thesheet-loosening air nozzles 494 due to the shape of the rear-endregulation plate 458, the escape portion 481 may be provided by cuttinga portion of the sheet-regulation surface 458 a that opposes thesheet-loosening air nozzles 494.

To cause the air to pass the rear-end regulation member 458 from the airblowing unit 406, as shown in FIG. 4B, an escape portion 481 b may beformed as a result of providing the sheet-regulation surface 458 a ofthe rear-end regulation plate 458 at a location that does not oppose theair blowing unit 406.

Accordingly, when the rear-end regulation plate 458 is formed into ashape or is disposed at a location that does not block the air that isblown out from the sheet-separation air nozzles 493 or thesheet-loosening air nozzles 494 of the air blowing unit 406, it ispossible to smoothen the flow of air.

Next, the example in which the through holes (escape portion) 481 a,instead of the escape portion 481 b, are formed in the rear-endregulation plate 458 will be described. As shown in FIGS. 5A and 5B, aretreating member 481 is provided at a top portion of the rear-endregulation plate 458 that is provided at the first paper deck 401.

The retreating member 481 is guided by a guiding member 458 b so as toslide obliquely at an angle of 45 degrees with respect to the rear-endregulation plate 458. A retreating spring 482 is disposed between therear-end regulation plate 458 and the retreating member 481. One end 482a of the retreating spring 482 is stopped by the body 458 a of therear-end regulation plate 458, and another end 482 b of the retreatingspring 482 is stopped by the retreating member 481.

As shown in FIG. 5A, by the action of the retreating spring 482, theretreating member 481 is extended upward. When, for example, anobstacle, such as the frame 151 of the sheet feeding device 400, existsas shown in FIG. 6, the retreating member 481 retreats by being pusheddownward by the obstacle as shown in FIG. 5B.

Here, as shown in FIGS. 5A and 5B, the retreating member 481 has thethrough holes 481 a that pass through the retreating member 481 in afront-back direction. The through holes 481 a allow the air from thesheet-separation nozzles 493 and the air from the sheet-loosening airnozzles 494 to flow smoothly between the sheets.

Accordingly, it is possible to cause the air to flow in a laminar statebetween the sheets that exist between the nozzles 493 and the rear-endregulation plate 458 and between the nozzles 494 and the rear-endregulation plate 458. The laminar flow of the air makes it possible toperform sheet loosening and separation with higher efficiency.

When the rear-end regulation plate 458 is positioned at a locationopposing the locations of the nozzles 493 and 494, that is, at alocation opposing the openings of the nozzles 493 and 494 in thesheet-feed direction, the through holes 481 a make it possible toperform sheet loosening and separation with even higher efficiency.

In the foregoing description, the rear-end regulation plate 458 is usedas a regulation member that regulates the positions of the sheets, andthe air blowing units 406 blow air from the front edges of sheet stackthat are stacked in the trays 403. However, the present invention is notlimited thereto. For example, when air is blown from side edges of thesheet stack that are stacked in the trays 403, escape portions 481 orthrough holes 481 a may be formed in the side regulation plates 458 thatregulate the positions of the side edges of the sheets.

Although, in the embodiment, the regulation member has an escape portion481 and through holes 481 a, the regulation member may have an escapeportion 481 b and through holes 481 a.

Although, in the embodiment, the sheet feeding unit transports sheets asa result of attracting the sheets to the attracting conveying belt 407,the present invention is not limited thereto. For example, the sheetfeeding unit may be one that blows air onto the side edges of the sheetstack for previously loosening the sheets to reliably feed the sheetswhen the sheets are separated by a sheet separating method other thanthat described above, such as a typical sheet separating method thatuses a reversing roller.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions.

This application claims the benefit of Japanese Application No.2006-093634 filed Mar. 30, 2006, which is hereby incorporated byreference herein in its entirety.

1. A sheet feeding device comprising: a tray adapted to support a stackof sheets, the tray further being adapted to be raised and lowered; aregulation member having a sheet-regulation surface, the regulationmember being adapted to regulate the position of the sheet stack as aresult of the sheet-regulation surface coming into contact with thesheet stack; an air blowing mechanism positioned opposing to theregulation member, wherein the air blowing mechanism is configured toblow air into an upper region of the sheet stack; and a sheet feedingmechanism adapted to feed the top-most sheet away from the sheet stack,wherein the regulation member is configured such that the blown airpasses through an escape portion, defined by the sheet-regulationsurface.
 2. The sheet feeding device according to claim 1, wherein theescape portion faces, in an opposing manner, the air blowing mechanism.3. The sheet feeding device according to claim 1, wherein the escapeportion of the sheet-regulation member defines at least one throughhole, at a location that faces the air blowing mechanism in an opposingmanner, the through hole configured to allow the blown air to pass therethrough such that the air passes through the regulation member.
 4. Thesheet feeding device according to claim 1, wherein escape portion isgenerally U-shaped and positioned at an upper portion of thesheet-regulation surface.
 5. The sheet feeding device according to claim1, wherein the air blowing mechanism has a plurality of nozzles forblowing the air from the upper region of the sheet stack towards theregulation member.
 6. An image forming apparatus comprising: a trayadapted to support a stack of sheets, the tray further adapted to beraised and lowered; a regulation member having a sheet-regulationsurface, the regulation member being adapted to regulate the position ofthe sheet stack as a result of the sheet-regulation surface coming intocontact with the sheet stack; an air blowing mechanism positionedopposing to the regulation member, wherein the air blowing mechanism isconfigured to blow air into an upper region of the sheet stack; a sheetfeeding mechanism adapted to feed the top-most sheet away from the sheetstack; and an image forming device that forms images on the sheets fedby the sheet feeding mechanism, wherein the regulation member isconfigured such that the blown air passes through an escape portion,defined by the sheet-regulation surface.